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A search for new phenomena in pp collisions at ?s=13TeV in final states with missing transverse momentum and at least one jet using the ?T variable
(Springer, 2017) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
A search for new phenomena is performed in final states containing one or more jets and an imbalance in transverse momentum in pp collisions at a centre-of-mass energy of 13 TeV. The analysed data sample, recorded with the CMS detector at the CERN LHC, corresponds to an integrated luminosity of 2.3 fb(-1). Several kinematic variables are employed to suppress the dominant background, multijet production, as well as to discriminate between other standard model and new physics processes. The search provides sensitivity to a broad range of new-physics models that yield a stable weakly interacting massive particle. The number of observed candidate events is found to agree with the expected contributions from standard model processes, and the result is interpreted in the mass parameter space of fourteen simplified supersymmetric models that assume the pair production of gluinos or squarks and a range of decay modes. For models that assume gluino pair production, masses up to 1575 and 975 GeV are excluded for gluinos and neutralinos, respectively. For models involving the pair production of top squarks and compressed mass spectra, top squark masses up to 400 GeV are excluded.
A search for pair production of new light bosons decaying into muons
(Elsevier, 2016) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
A search for the pair production of new light bosons, each decaying into a pair of muons, is performed with the CMS experiment at the LHC, using a dataset corresponding to an integrated luminosity of 20.7 fb(-1) collected in proton-proton collisions at center-of-mass energy of root s = 8 TeV. No excess is observed in the data relative to standard model background expectation and a model independent upper limit on the product of the cross section, branching fraction, and acceptance is derived. The results are compared with two benchmark models, the first one in the context of the next-to-minimal super-symmetric standard model, and the second one in scenarios containing a hidden sector, including those predicting a nonnegligible light boson lifetime. (C) 2015 CERN for the benefit of the CMS Collaboration. Published by Elsevier B.V.
Alignment of the CMS tracker with LHC and cosmic ray data
(Iop Publishing Ltd, 2014) Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; The CMS Collaboration
The central component of the CMS detector is the largest silicon tracker ever built. The precise alignment of this complex device is a formidable challenge, and only achievable with a significant extension of the technologies routinely used for tracking detectors in the past. This article describes the full-scale alignment procedure as it is used during LHC operations. Among the specific features of the method are the simultaneous determination of up to 200 000 alignment parameters with tracks, the measurement of individual sensor curvature parameters, the control of systematic misalignment effects, and the implementation of the whole procedure in a multiprocessor environment for high execution speed. Overall, the achieved statistical accuracy on the module alignment is found to be significantly better than 10 mu m.
Angular analysis and branching fraction measurement of the decay B0 ? K*0?+?-
(Elsevier, 2013) Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; The CMS Collaboration
The angular distributions and the differential branching fraction of the decay B-0 -> K*(892)(0)mu(+)mu(-) are studied using a data sample corresponding to an integrated luminosity of 5.2 fb(-1) collected with the CMS detector at the LHC in pp collisions at root s = 7 TeV. From more than 400 signal decays, the forward-backward asymmetry of the muons, the K*(892)(0) longitudinal polarization fraction, and the differential branching fraction are determined as a function of the square of the dimuon invariant mass. The measurements are in good agreement with standard model predictions. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved.
Angular analysis of the decay B0 ? K*0?+?- from pp collisions at ?s=8 TeV
(Elsevier, 2016) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
The angular distributions and the differential branching fraction of the decay B-0 -> K*(892)(0)mu(+)mu(-) are studied using data corresponding to an integrated luminosity of 20.5 fb(-1) collected with the CMS detector at the LHC in pp collisions at root s = 8 TeV. From 1430 signal decays, the forward-backward asymmetry of the muons, the K*(892)(0) longitudinal polarization fraction, and the differential branching fraction are determined as a function of the dimuon invariant mass squared. The measurements are among the most precise to date and are in good agreement with standard model predictions. (C) 2015 CERN for the benefit of the CMS Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Angular coefficients of Z bosons produced in pp collisions at ?S=8 TeV and decaying to ?+?- as a function of transverse momentum and rapidity
(Elsevier, 2015) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; The CMS Collaboration
Measurements of the five most significant angular coefficients, A(0) through A(4), for Z bosons produced in pp collisions at root S = 8 TeV and decaying to mu(+)mu(-) are presented as a function of the transverse momentum and rapidity of the Z boson. The integrated luminosity of the dataset collected with the CMS detector at the LHC corresponds to 19.7 fb(-1). These measurements provide comprehensive information about the Z boson production mechanisms, and are compared to the QCD predictions at leading order, next-to-leading order, and next-to-next-to-leading order in perturbation theory. (C) 2015 CERN for the benefit of the CMS Collaboration. Published by Elsevier B.V.
Azimuthal anisotropy of charged particles with transverse momentum up to 100GeV/c in PbPb collisions at ?SNN=5.02 TeV
(Elsevier, 2018) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; The CMS Collaboration
The Fourier coefficients v(2) and v(3) characterizing the anisotropy of the azimuthal distribution of charged particles produced in PbPb collisions at root S-NN = 5.02 TeV are measured with data collected by the CMS experiment. The measurements cover a broad transverse momentum range, 1 < p(T) < 100 GeV/c. The analysis focuses on the p(T) > 10 GeV/c range, where anisotropic azimuthal distributions should reflect the path-length dependence of parton energy loss in the created medium. Results are presented in several bins of PbPb collision centrality, spanning the 60% most central events. The v(2) coefficient is measured with the scalar product and the multiparticle cumulant methods, which have different sensitivities to initial-state fluctuations. The values from both methods remain positive up to p(T) similar to 60-80 GeV/c, in all examined centrality classes. The v(3) coefficient, only measured with the scalar product method, tends to zero for p(T) greater than or similar to 20 GeV/c. Comparisons between theoretical calculations and data provide new constraints on the path-length dependence of parton energy loss in heavy ion collisions and highlight the importance of the initial-state fluctuations. (C) 2017 The Author. Published by Elsevier B.V.
Azimuthal correlations for inclusive 2-jet, 3-jet, and 4-jet events in pp collisions at ?s=13 TeV
(Springer, 2018) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; The CMS Collaboration
Azimuthal correlations between the two jets with the largest transverse momenta p(T) in inclusive 2-, 3-, and 4-jet events are presented for several regions of the leading jet p(T) up to 4 TeV. For 3- and 4-jet scenarios, measurements of the minimum azimuthal angles between any two of the three or four leading p(T) jets are also presented. The analysis is based on data from proton-proton collisions collected by the CMS Collaboration at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). Calculations based on leading-order matrix elements supplemented with parton showering and hadronization do not fully describe the data, so next-to-leading-order calculations matched with parton shower and hadronization models are needed to better describe the measured distributions. Furthermore, we show that azimuthal jet correlations are sensitive to details of the parton showering, hadronization, and multiparton interactions. Anext-to-leading-order calculation matched with parton showers in the MC@NLO method, as implemented in HERWIG 7, gives a better overall description of the measurements than the powheg method.
Azimuthal decorrelation of jets widely separated in rapidity in pp collisions at ?s=7 TeV
(Springer, 2016) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
The decorrelation in the azimuthal angle between the most forward and the most backward jets (Mueller-Navelet jets) is measured in data collected in pp collisions with the CMS detector at the LHC at root s = 7 TeV. The measurement is presented in the form of distributions of azimuthal-angle differences, Delta phi, between the Mueller-Navelet jets, the average cosines of (pi - Delta phi), 2(pi - Delta phi), and 3(pi - Delta phi), and ratios of these cosines. The jets are required to have transverse momenta, p(T), in excess of 35 GeV and rapidities, |y|, of less than 4.7. The results are presented as a function of the rapidity separation, Delta y, between the Mueller-Navelet jets, reaching Delta y up to 9.4 for the first time. The results are compared to predictions of various Monte Carlo event generators and to analytical predictions based on the DGLAP and BFKL parton evolution schemes.
Bose-Einstein correlations in pp, pPb, and PbPb collisions at ?sNN=0.9-7 TeV
(Amer Physical Soc, 2018) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; The CMS Collaboration
Quantum-statistical (Bose-Einstein) two-particle correlations are measured in pp collisions at root s = 0.9, 2.76, and 7 TeV, as well as in pPb and peripheral PbPb collisions at nucleon-nucleon center-of-mass energies of 5.02 and 2.76 TeV, respectively, using the CMS detector at the Large Hadron Collider. Separate analyses are performed for same-sign unidentified charged particles as well as for same-sign pions and kaons identified via their energy loss in the silicon tracker. The characteristics of the one-, two-, and three-dimensional correlation functions are studied as functions of the pair average transverse momentum (k(T)) and the charged-particle multiplicity in the event. For all systems, the extracted correlation radii steadily increase with the event multiplicity, and decrease with increasing k(T). The radii are in the range 1-5 fm, the largest values corresponding to very high multiplicity pPb interactions and to peripheral PbPb collisions with multiplicities similar to those seen in pPb data. It is also observed that the dependencies of the radii on multiplicity and k(T) largely factorize. At the same multiplicity, the radii are relatively independent of the colliding system and center-of-mass energy.
Charged-particle nuclear modification factors in PbPb and pPb collisions at ?sNN=5.02 TeV
(Springer, 2017) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
The spectra of charged particles produced within the pseudorapidity window vertical bar eta vertical bar < 1 at root s(NN) = 5 : 02 TeV are measured using 404 mu b(-1) of PbPb and 27.4 pb(-1) of pp data collected by the CMS detector at the LHC in 2015. The spectra are presented over the transverse momentum ranges spanning 0 : 5 < p(T) < 400 GeV in pp and 0 : 7 < p(T) < 400 GeV in PbPb collisions. The corresponding nuclear modification factor, R-AA, is measured in bins of collision centrality. The R-AA in the 5% most central collisions shows a maximal suppression by a factor of 7-8 in the p(T) region of 6-9 GeV. This dip is followed by an increase, which continues up to the highest p(T) measured, and approaches unity in the vicinity of p(T) = 200 GeV. The R-AA is compared to theoretical predictions and earlier experimental results at lower collision energies. The newly measured pp spectrum is combined with the pPb spectrum previously published by the CMS collaboration to construct the pPb nuclear modification factor, R-pA, up to 120 GeV. For p(T) > 20 GeV, R-pA exhibits weak momentum dependence and shows a moderate enhancement above unity.
Coherent J/? photoproduction in ultra-peripheral PbPb collisions at ?sNN=2.76 TeV with the CMS experiment
(Elsevier, 2017) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
The cross section for coherent J/psi photoproduction accompanied by at least one neutron on one side of the interaction point and no neutron activity on the other side, Xn0n, is measured with the CMS experiment in ultra-peripheral PbPb collisions at root sNN= 2.76TeV. The analysis is based on a data sample corresponding to an integrated luminosity of 159 mu b(-1), collected during the 2011 PbPb run. The J/psi mesons are reconstructed in the dimuon decay channel, while neutrons are detected using zero degree calorimeters. The measured cross section is d sigma(Xn)o(n)(coh)/dy(J/psi) = 0.36 +/- 0.04 (stat)+/- 0.04 (syst) mbin the rapidity interval 1.8
Combination of searches for heavy resonances decaying to WW, WZ, ZZ, WH, and ZH boson pairs in proton-proton collisions at ?s=8 and 13 TeV
(Elsevier, 2017) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; The CMS Collaboration
A statistical combination of searches is presented for massive resonances decaying to WW, WZ, ZZ, WH, and ZH boson pairs in proton-proton collision data collected by the CMS experiment at the LHC. The data were taken at centre-of-mass energies of 8 and 13TeV, corresponding to respective integrated luminosities of 19.7 and up to 2.7 fb(-1). The results are interpreted in the context of heavy vector triplet and singlet models that mimic properties of composite-Higgs models predicting W' and Z' bosons decaying to WZ, WW, WH, and ZH bosons. A model with a bulk graviton that decays into WW and ZZ is also considered. This is the first combined search for WW, WZ, WH, and ZH resonances and yields lower limits on masses at 95% confidence level for W' and Z' singlets at 2.3 TeV, and for a triplet at 2.4TeV. The limits on the production cross section of a narrow bulk graviton resonance with the curvature scale of the warped extra dimension (K)over-tilde = 0.5, in the mass range of 0.6 to 4.0TeV, are the most stringent published to date. (c) 2017 The Author(s). Published by Elsevier B.V.
Combined search for electroweak production of charginos and neutralinos in proton-proton collisions at ?s=13 TeV
(Springer, 2018) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; The CMS Collaboration
A statistical combination of several searches for the electroweak production of charginos and neutralinos is presented. All searches use proton-proton collision data at A root s = 13 TeV, recorded with the CMS detector at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb(-1). In addition to the combination of previous searches, a targeted analysis requiring three or more charged leptons (electrons or muons) is presented, focusing on the challenging scenario in which the difference in mass between the two least massive neutralinos is approximately equal to the mass of the Z boson. The results are interpreted in simplified models of chargino-neutralino or neutralino pair production. For chargino-neutralino production, in the case when the lightest neutralino is massless, the combination yields an observed (expected) limit at the 95% confidence level on the chargino mass of up to 650 (570) GeV, improving upon the individual analysis limits by up to 40 GeV. If the mass difference between the two least massive neutralinos is approximately equal to the mass of the Z boson in the chargino-neutralino model, the targeted search requiring three or more leptons obtains observed and expected exclusion limits of around 225 GeV on the second neutralino mass and 125 GeV on the lightest neutralino mass, improving the observed limit by about 60 GeV in both masses compared to the previous CMS result. In the neutralino pair production model, the combined observed (expected) exclusion limit on the neutralino mass extends up to 650-750 (550-750) GeV, depending on the branching fraction assumed. This extends the observed exclusion achieved in the individual analyses by up to 200 GeV. The combined result additionally excludes some intermediate gaps in the mass coverage of the individual analyses.
Comparison of the Z/?* + jets to ? + jets cross sections in pp collisions at ?s = 8 (vol 10, 128, 2015)
(Springer, 2016) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
[Abstract Not Available]
Comparison of the Z/?* plus jets to ? plus jets cross sections in pp collisions at ?s=8 TeV
(Springer, 2015) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; The CMS Collaboration
A comparison of the differential cross sections for the processes Z/gamma* + jets and photon (gamma)+ jets is presented. The measurements are based on data collected with the CMS detector at root s = 8TeV corresponding to an integrated luminosity of 19.7 fb(-1). The differential cross sections and their ratios are presented as functions of p(T). The measurements are also shown as functions of the jet multiplicity. Differential cross sections are obtained as functions of the ratio of the Z/gamma* p(T) to the sum of all jet transverse momenta and of the ratio of the Z/gamma* p(T) to the leading jet transverse momentum. The data are corrected for detector effects and are compared to simulations based on several QCD calculations.
Constraints on anomalous Higgs boson couplings using production and decay information in the four-lepton final state
(Elsevier, 2017) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; The CMS Collaboration
A search is performed for anomalous interactions of the recently discovered Higgs boson using matrix element techniques with the information from its decay to four leptons and from associated Higgs boson production with two quark jets in either vector boson fusion or associated production with a vector boson. The data were recorded by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 38.6 fb(-1). They are combined with the data collected at center-of-mass energies of 7 and 8 TeV, corresponding to integrated luminosities of 5.1 and 19.7 fb(-1), respectively. All observations are consistent with the expectations for the standard model Higgs boson. (C) 2017 The Author. Published by Elsevier B.V.
Constraints on parton distribution functions and extraction of the strong coupling constant from the inclusive jet cross section in pp collisions at ?s=7TeV
(Springer, 2015) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; The CMS Collaboration
The inclusive jet cross section for proton-proton collisions at a centre-of-mass energy of 7 TeV was measured by the CMS Collaboration at the LHC with data corresponding to an integrated luminosity of 5.0 fb(-1). The measurement covers a phase space up to 2 TeV in jet transverse momentum and 2.5 in absolute jet rapidity. The statistical precision of these data leads to stringent constraints on the parton distribution functions of the proton. The data provide important input for the gluon density at high fractions of the proton momentum and for the strong coupling constant at large energy scales. Using predictions from perturbative quantum chromodynamics at next-to-leading order, complemented with electroweak corrections, the constraining power of these data is investigated and the strong coupling constant at the Z boson mass M-Z is determined to be alpha(S)(M-Z) = 0.1185 +/- 0.0019 (exp)(-0.0037)(+0.0060) (theo), which is in agreement with the world average.
Constraints on the chiral magnetic effect using charge-dependent azimuthal correlations in pPb and PbPb collisions at the CERN Large Hadron Collider
(Amer Physical Soc, 2018) Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Ambrogi, F.; Asilar, E.; Bergauer, T.; The CMS Collaboration
Charge-dependent azimuthal correlations of same-and opposite-sign pairs with respect to the second-and third-order event planes have been measured in pPb collisions at root s(NN) = 8.16 TeV and PbPb collisions at 5.02 TeV with the CMS experiment at the LHC. The measurement is motivated by the search for the charge separation phenomenon predicted by the chiral magnetic effect (CME) in heavy ion collisions. Three-and two-particle azimuthal correlators are extracted as functions of the pseudorapidity difference, the transverse momentum (p(T)) difference, and the p(T) average of same-and opposite-charge pairs in various event multiplicity ranges. The data suggest that the charge-dependent three-particle correlators with respect to the second-and third-order event planes share a common origin, predominantly arising from charge-dependent two-particle azimuthal correlations coupled with an anisotropic flow. The CME is expected to lead to a v(2)-independent three-particle correlation when the magnetic field is fixed. Using an event shape engineering technique, upper limits on the v(2)-independent fraction of the three-particle correlator are estimated to be 13% for pPb and 7% for PbPb collisions at 95% confidence level. The results of this analysis, both the dominance of two-particle correlations as a source of the three-particle results and the similarities seen between PbPb and pPb, provide stringent constraints on the origin of charge-dependent three-particle azimuthal correlations and challenge their interpretation as arising from a chiral magnetic effect in heavy ion collisions.
Constraints on the Higgs boson width from off-shell production and decay to Z-boson pairs
(Elsevier, 2014) Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Bergauer, T.; Dragicevic, M.; The CMS Collaboration
Constraints are presented on the total width of the recently discovered Higgs boson, Gamma(H), using its relative on-shell and off-shell production and decay rates to a pair of Z bosons, where one Z boson decays to an electron or muon pair, and the other to an electron, muon, or neutrino pair. The analysis is based on the data collected by the CMS experiment at the LHC in 2011 and 2012, corresponding to integrated luminosities of 5.1 fb(-1) at a center-of-mass energy root s = 7 TeV and 19.7 fb(-1) at root s = 8 TeV. A simultaneous maximum likelihood fit to the measured kinematic distributions near the resonance peak and above the Z-boson pair production threshold leads to an upper limit on the Higgs boson width of Gamma(H) < 22 MeV at a 95% confidence level, which is 5.4 times the expected value in the standard model at the measured mass of m(H) = 125.6 GeV. (C) 2014 The Authors. Published by Elsevier B.V.

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